blink filter

[davebraze]

Write a function to remove fixations on either side of a blink. In SRR systems, blinks are always flanked by saccade artifacts. The fixations right before/after those saccades should be removed under some conditions. The SRR manual variously suggests removing these fixations if they are >100ms or >120ms in duration.

Need a function to remove such fixations with a reasonable default value for maximum duration of fixations to filter.

We also want to include a count of the number of blinks in a particular recording period.